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p-task.htm
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gah: More documentation on multi-tasking.
Index: p-task.htm
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width="32" height="32"> Win32Forth</h1>
<hr /><h1>Using the Task Wordset
! </h1><hr /><p>Multi-tasking in Win32Forth is accomplished by using the Windows<sub>® </sub> multi-tasker.
This is a pre-emptive multi-tasker.
</p><h2>Glossary
</h2><pre><b><a name="0">cell field+ task>parm ( task-block -- addr ) \ W32F Task
--- 17,53 ----
width="32" height="32"> Win32Forth</h1>
<hr /><h1>Using the Task Wordset
! </h1><hr /><p>The multi-tasker is not loaded in the system by default so the file TASK.F in the lib
! folder should be included in any program that multi-tasks, unless using the file
! MULTITHR.F (also in the lib folder) which includes it automatically.
! </p><p>Multi-tasking in Win32Forth is accomplished by using the Windows<sub>® </sub> multi-tasker.
This is a pre-emptive multi-tasker.
+ </p><h2>The Task Control Block
+ </h2><p>The task control block (also known as task-block or TCB) is a small structure either
+ alloted in the dictionary or allocated on the heap containing information about a task.
+ </p><ul><li>The xt and parameter variables are set when the task-block is created.
+ </li><li>The stop flag can be set by other tasks and is used to signal the task that it has
+ been asked to finish.
+ </li><li>The ID is set when the task is created and is valid only until the task terminates.
+ </li><li>The handle is set when the task is created and is valid until it is closed by the
+ API CloseHandle function, even after the task has terminated. The operating system
+ does not free the OS resources allocated to a task until all handles (except for
+ the pseudohandle returned by the API GetCurrentThread) are closed and
+ the task has terminated. Programs should close the handle as soon as it's no longer
+ needed (if it's never used close it at the start of the task word).
+ </li></ul><h2>The User Area
+ </h2><p>When a task is created the operating system allocates a stack for the task.
+ Win32Forth splits this stack into three regions, a return stack, a User area
+ and a data stack. The address of this User area is stored in thread local
+ storage so that callbacks have access to the correct User area for the task
+ (Versions prior to V6.05 always used the main task's User area for callbacks).
+ When a task starts the contents of the User area are undefined except
+ </p><ul><li>Base is set to decimal.
+ </li><li>The exception handler is set so the task exits if an exception is thrown, returning
+ the error code to the operating system.
+ </li><li>TCB is set to the task control block of the task.
+ </li><li>RP0 is set to the base of the return stack.
+ </li><li>SP0 is set to the base of the data stack.
+ </li></ul><p>All other User variables used by a task should be explicitly set before use.
+ If the task uses floating-point words then FINIT should be called first.
</p><h2>Glossary
</h2><pre><b><a name="0">cell field+ task>parm ( task-block -- addr ) \ W32F Task
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